A field controller unit is, in general, a controller configured to control, monitor, and manage equipment of an HVAC system in or around a building or building area. The field controller unit may typically include a base that mounts to a control panel or piece of equipment and a head unit or field controller that attaches to the base. However, to update the hardware of the field controller traditionally requires replacing the entire field controller unit or painstakingly wiring a new field controller to the original base as the new field controller may not mate with the original base.